Various vaccines have been developed and used to prevent and treat a wide variety of diseases including viral diseases. However, when an antigen such as a viral protein is administered alone into a living body, stability of the antigen molecule in the living body is low, and efficiency of incorporation thereof into cells is insufficient. Then, efforts have been made in current vaccine therapies, for example, by administering a mixture formed by emulsification with an appropriate particulate carrier or immunostimulatory agent (adjuvant). However, for example, there has been no report of a case in which a preexisting adjuvant is successfully used for an HTLV-1 vaccine in an HTLV-1 infection. This is because the activity of cytotoxic T lymphocytes (CTLs) against HTLV-1 and frequency of existence thereof in a living body are low. Furthermore, for example, attempts have been made to treat an infection with a virus such as HIV or a cancer in a patient by inducing CTLs which attack specifically the infected cells or cancer cells. In such treatment, it is considered to be important whether CTLs can be induced effectively. For this purpose, an adjuvant such as Freund's adjuvant or aluminum hydroxide is usually used. However, no satisfactory result in respect of the safety or efficacy has been achieved. Thus, it is has not been reported that a polyamino acid, in particular poly(γ-glutamic acid), exhibits an excellent effect as an adjuvant as described herein.
Recently, researches on and development of nanoparticles have been promoted because the nanoparticles are expected to play novel roles in various fields due to their size. Attempts have also been made to utilize nanoparticles for therapies. For example, a nanoparticle is used as a carrier for a drug in some studies (see Patent Documents 1 and 2). However, there is concern for the influence of the nanoparticle on a living body, because its behavior in the body has not yet been elucidated and, therefore, the toxicity or safety is uncertain. It is essential for the actual contribution to medical service to practically develop a biodegradable nanoparticle that can substitute for the undegradable nanoparticles. There has also been concerned that the activity of an antigen is lost, for example, by denaturation or degradation upon binding of the antigen to a nanoparticle, and the nanoparticle can not exhibit the function as an adjuvant. Thus, there has been no report on use, as an adjuvant, of a polyamino acid, in particular poly(γ-glutamic acid), that is prepared as a nanoparticle, a nanoparticle to which an antigen is immobilized, or use thereof as a vaccine as described herein.
Patent Document 1: JP-A-92870/1994
Patent Document 2: JP-A-256220/1994